The disclosure relates to (1aR,12bS)-8-cyclohexyl-11-fluoro-N-((1-methylcyclopropyl)sulfonyl)-1a-((3-methyl-3,8-diazabicyclo[3.2.1]oct-8-yl)carbonyl)-1,1a,2,12b-tetrahydrocyclopropa[d]indolo[2,1-a][2]benzazepine-5-carboxamide (Compound 1, formula I), including pharmaceutically acceptable salts, as well as compositions and methods of using the compound. The compound has activity against hepatitis C virus (HCV) and may be useful in treating those infected with HCV.
Hepatitis C virus (HCV) is a major human pathogen, infecting an estimated 170 million persons worldwide. Hepatitis C virus (HCV) is the most common bloodborne infection in the USA and worldwide and is the leading cause of liver transplantation (Eric Chak et.al. Liver International 2011, 1090-1101) A substantial fraction of these HCV infected individuals develop serious progressive liver disease, including cirrhosis and hepatocellular carcinoma (Lauer, G. M.; Walker, B. D. N. Engl. J. Med. 2001, 345, 41-52).
HCV is a positive-stranded RNA virus. Considerable heterogeneity is found within the nucleotide and encoded amino acid sequence throughout the HCV genome. At least six major genotypes have been characterized, and more than 50 subtypes have been described adding to the need for new therapies.
The genome consists of approximately 9500 nucleotides and has a single open reading frame (ORF) encoding a single large polyprotein of about 3000 amino acids. In infected cells, this polyprotein is cleaved at multiple sites by cellular and viral proteases to produce the structural and non-structural (NS) proteins. The NS proteins (NS3, NS4A, NS4B, NS5A, and NS5B) are required for viral RNA replication. NS3 is a serine protease that mediates cleavage of the polyprotein. The NS4A protein is a cofactor for the NS3 protease. The complex formation of the NS3 protein with NS4A seems necessary to the processing events, enhancing the proteolytic efficiency at all of the sites. The NS3 protein also exhibits nucleoside triphosphatase and RNA helicase activities. NS5B (also referred to as HCV polymerase) is a RNA-dependent RNA polymerase that is involved in the replication of HCV. The NS5B RNA-dependent RNA polymerase (RdRp) is essential to the replication cycle of HCV (Tomei L, Altamura S, Paonessa G, et al. Antivir Chem Chemother 2005, 16, 225-245). The HCV NS5B protein is described in “Structural Analysis of the Hepatitis C Virus RNA Polymerase in Complex with Ribonucleotides (Bressanelli; S. et al., Journal of Virology 2002, 3482-3492; and Defrancesco and Rice, Clinics in Liver Disease 2003, 7, 211-242. The NS5B crystal structure reveals a typical right-handed polymerase containing thumb, palm and finger domains surrounding the active site. (Lesburg C. A., Cable, M. B., Ferrari, et al. Nat Struc Biol 1999, 6, 937-943.) NS5B is the catalytic enzyme responsible for RNA replication and participates in higher order complexes at intracellular lipid membranes in association with various viral proteins and nucleic acids as well as host proteins. (El Hage N and Luo G. J Gen Virol 2003, 84, 2761-2769. Gao L, Aizaki H, He J W, et al. J Virol 2004, 78, 3480-3488) Examples of NS5B protein-protein interactions include binding to the NS3 helicase domain, facilitating RNA unwinding, and binding to the NS5A protein, a regulator of viral replication. (Jennings, et al. Biochemistry 2008, 47, 1126-1135. McCormick C J, Brown D, Griffin S, et al. J Gen Virol 2006, 87(Pt 1), 93-102).
HCV NS5B polymerase inhibitors can be divided into two classes based on their mode of inhibition: nucleoside (NUC) inhibitors compete with natural substrates and non-nucleoside inhibitors (NNI) are non-competitive allosteric inhibitors. Both NUC inhibitors and NNI have clinical proof of principal of antiviral activity via inhibition of the NS5B target (Gelman, M A. and J S. Glenn (2011) Mixing the right hepatitis C inhibitor cocktail. Trends in Molecular Medicine 17:1, 34-46; Soriano V., E. Vispo, E. Poveda, P. Labarga, L. Martin-Carbonero, J V. Fernandez-Montero and P. Barreiro (2011) Directly acting antivirals against hepatitis C virus. J Antimicrob Chemother 66, 1673-1686). NNI prevent conformational transitions of the polymerase that are required for the initiation of RNA synthesis (Ma H., V. Leveque, A. De Witte, W. Li, T. Hendricks, S M. Clausen, N. Cammack, K. Klumpp. (2005) Inhibition of native hepatitis C virus replicase by nucleotide and non-nucleoside inhibitors. Virology 332, 8-15). Co-crystals of NNI show that they bind to one of at least three distinct sites on the polymerase, consistent with the diverse patterns of resistance observed for these inhibitors in vitro and in vivo (Beaulieu, P. (2009) Recent advances in the development of NS5B polymerase inhibitors for the treatment of hepatitis C virus infection. Expert Opinion on Therapeutic Patents. 19, 145-64). These studies substantiate observations in the HCV RNA replicon system in which inhibition of NS5B blocks viral replication. (Tomei L, Altamura S, Paonessa G, et al. Antivir Chem Chemother 2005, 16, 225-245).
Previously, the most effective HCV therapy employed a combination of alpha-interferon and ribavirin, leading to sustained efficacy in only 40% of genotype 1 patients (Poynard, T. et al. Lancet 1998, 352, 1426-1432). Clinical results demonstrate that pegylated alpha-interferon is superior to unmodified alpha-interferon as monotherapy (Zeuzem, S. et al. N. Engl. J. Med. 2000, 343, 1666-1672). However, even with experimental therapeutic regimens involving combinations of pegylated alpha-interferon and ribavirin, a substantial fraction of patients did not have a sustained reduction in viral load. In 2011, improved therapies for genotype 1 patients that include an HCV NS3 protease inhibitor, a small molecule direct acting antiviral (DAA), plus interferon and ribavirin were approved by FDA. Two protease inhibitors (INCIVEK™ (Telaprevir) and VICTRELIS™ (Boceprevir) were approved; thus a choice of drug exists for combination therapy with interferon and ribavirin. (Ghany, M G., D R. Nelson, D B. Strader, D L. Thomas, and L B. Seeff. (2011) An Update on Treatment of Genotype 1 Chronic Hepatitis C Virus Infection: 2011 Practice Guideline by the American Association for the Study of Liver Diseases. Hepatology, 54(4): 1433-1444).
Currently, significant research efforts are focused on further improvement of cure rates, by improving tolerability, addressing the needs of patients whose virus or genetic markers make their disease less responsive to interferon based therapy, and shortening duration of therapy. Interferons with fewer side effects and interferon free regimens of small molecule DAA combinations are being tested. Because of the rapid replication rate and development of resistance by HCV, it is believed that treatment regimens will necessarily be combinations of agents.
Hepatitis C infected patients typically have a long (>10 years) asymptomatic phase of disease that occurs before substantial hepatic injury and symptoms are manifested. For this reasons, HCV infected individuals initially maintain a high quality of life or may not even know they are infected. Since all currently approved treatments include interferon and ribavirin which are associated with serious side effects, and since the recently approved protease inhibitors are associated with additional side effects (rash and anemia), many HCV infected patients choose to delay therapy until more acceptable regimens, expected within this decade, are approved. In the future, agents that have actual or perceived serious liabilities, such as risk for causing cardiovascular events or severe hepatotoxicity, will not be widely utilized for therapy. Thus, current research is focused on the development of safe and effective inhibitor combinations that can deliver a cure for HCV infection in the absence of interferon. Considerable efforts aimed at identifying direct acting antiviral agents which inhibit Hepatitis C virus replication have been disclosed in the art. (Gelman, M A. and J S. Glenn (2011) Mixing the right hepatitis C inhibitor cocktail. Trends in Molecular Medicine 17:1, 34-46; Soriano V., E. Vispo, E. Poveda, P. Labarga, L. Martin-Carbonero, J V. Fernandez-Montero and P. Barreiro (2011) Directly acting antivirals against hepatitis C virus. J Antimicrob Chemother 66, 1673-1686.
The general methodology used by pharmaceutical companies to identify compounds that have the potential to be used in the treatment of HCV in human patients is similar to the methodology applied to other drug discovery targets. Initial assessment of potency vs. the therapeutic target (in this case the NS5B enzyme targeted for inhibition of hepatitis C) is done with enzyme and cell based assays. Compounds with acceptable potency are profiled in additional in vitro assays to assess their suitability for achieving good pharmacokinetic (PK) profiles in animal models (rodent or higher species). Examples are (i) in vitro assays to assess metabolic stability in the presence of microsomal membranes prepared from liver cells of human and other species, and (ii) permeability assay systems such as Caco-2 or PAMPA to assess the potential for absorption. In vitro assays such as general cytotoxicity and cytochrome P450 enzyme inhibition (indicates the potential for drug-drug interactions) are also used to assess potential safety liabilities.
One serious liability which all drug discovery programs have developed in vitro strategies to avoid is the prolongation of myocardial repolarization and lengthening the QT interval on the electrocardiogram, as these properties have been associated with an increased risk for the development of life-threatening ventricular arrhythmias and death. Compounds with this liability would obviously not be useful for the treatment of Hepatitis C. In almost every case, drugs that increase the QT interval also block a specific potassium channel [human Ether-a-go-go Related Gene (hERG)] in in vitro assays. The prolongation of repolarization is of particular importance because it has been associated with an increased risk for the subsequent development of malignant ventricular arrhythmias and death. In the presence of prolonged myocardial repolarization, some individuals may develop a distinct form of ventricular tachycardia known as torsades de pointes. The development of such drug related new or worsened ventricular arrhythmias is termed proarrhythmia. Routine in vitro assays include hERG potassium ion channel assays (in silico, high-throughput flux and patch-clamp electrophysiology) and a Purkinje fiber action potential assay. The hERG screens will identify compounds that likely will affect the cardiac rapidly activating delayed rectifier potassium current (IKr). Most drugs that prolong cardiac repolarization do so by blocking this current.
For compounds in clinical development where therapeutic exposures are known, experts have estimated that a margin of 30-fold or greater between hERG IC50 and the therapeutic Cmax of compound not bound to protein could be sufficient for safety from hERG-mediated arrhythmias associated with QTc prolongation; although Redfern et al. suggest that increasing the margin even further would be prudent. (Redfern, W. S.; Carlsson, L.; Davis, A. S.; Lynch, W. G.; MacKenzie, I.; Palethorpe, S.; Siegl, P. K. S.; Strang, I.; Sullivan, A. T.; Wallis, R.; Camm, A. J.; Hammond, T. G. Relationships between preclinical cardiac electrophysiology, clinical QT interval prolongation and torsade de pointes for a broad range of drugs: evidence for a provisional safety margin in drug development. Cardiovascular Research (2003), 58(1), 32-45. De Bruin, M. L.; Pettersson, M.; Meyboom, R. H. B.; Hoes, A. W.; Leufkens, H. G. M. Anti-HERG activity and the risk of drug-induced arrhythmias and sudden death. European Heart Journal (2005), 26(6), 590-597). For the assessment of risk in preclinical programs, some guidelines have been developed by ICH (International Conference On Harmonisation Of Technical Requirements For Registration Of Pharmaceuticals For Human Use), and these are also provided on the FDA web site for guidance to industry. An excerpt of a pertinent section (2.2) on profiling preclinical compounds follows: 2.2. ICH S7B strategy: The chemical class of drug candidates determines the preclinical safety strategy. The golden standard for the in vitro IKr assay is the test for HERG interaction by means of patch-clamp studies. The in vivo telemetry assay allows the study of QT interval with integrated risk assessment. For in vitro cardiac action potential duration (APD) studies multicellular preparation from animal heart is needed to study potential adverse effects of drug candidates on the whole concert of cardiac voltage-gated ion channels.
For in vitro assessment the gold standard (patch clamp assay) is also used to meet FDA regulatory recommendations (hERG assay); however, this assay is low through-put and in silico and high-throughput flux (flipr) assays are used for initial screening of greater numbers of compounds. Flux results (flipr) are validated with the patch clamp assay.
Because in vivo assessments such as telemetry in animals are so labor intensive and costly, they are employed exclusively for compounds of interest with respect to the entire compound profile. These are compounds for which in vitro assays suggest there is a high likelihood they could continue to advance if profiled further. Alternatively, compounds used to provide a benchmark to validate in vitro assays may be assessed in vivo. This holds true for advanced in vitro APD studies as well. Purkinje fiber testing is also low-throughput and complements the hERG assay by assessing all of the major ionic currents which contribute to the cardiac action potential. Signals for effects on other cardiac ionic currents can be detected in this action potential assay and followed-up in patch-clamp studies on candidate cardiac ion channels (e.g. Na, Ca or other K channels such as Iks).
A number of compounds which are inhibitors of HCV NS5B are in clinical development or have advanced to clinical studies and been discontinued for various reasons. More specific to this application, HCV NS5B inhibitors which bind to a site referred to in the art as Site 1 have been disclosed in U.S. Pat. Nos. 7,399,758, 7,485,633 and published U.S. patent application 2009130057.
The novel compound of the present invention which falls within the definition of Formula I in US application publication 2009130057 is not disclosed or described in that application. Surprisingly, it has been discovered that (2R)-2-[[(4-chlorophenyl)sulfonyl][[2-fluoro-4-(1,2,4-oxadiazol-3-yl)phenyl]methyl]amino]-5,5,5-trifluoropentanamide possesses unique attributes which make it useful for the treatment of hepatitis C.